Where's Frisk?
by thetrueninjagofan12
Summary: Frisk gets kidnapped and Sans does what he can to save her. I DON'T OWN UNDERTALE! Rated T for blood and bad language
1. Chapter 1: dissapearance

It was a beautiful day on the surface. Birds were singing, flowers were blooming, it was days days like this where kids like Frisk-

"Bye Sans, bye Papyrus."

"Have a good day kiddo."

-Should be going to school. It was a nice walk to school though. Frisk was humming her favorite tune, skipping joyfully. About half way, she met up with Monster kid.

"Hi Frisk!" He greeted her, in his usual bubbly tone.

"Hey MK. What's up?"

Then they walked. School was fine enough, although Frisk loved having Toriel as a teacher, it was a little awkward. She often called her "My child" even though Sans was the one who adopted her. Sans may legally be her father, but he told her not to consider himself as such. Instead he told her to refer to him and Papyrus as her brothers. Anyways, Frisk loved school, but it was too easy for her. Because the monsters never went to school, Toriel taught basic math, English. Etc. Frisk learned this stuff a long time ago and often leads to her getting bored. This also sometimes leads to her getting in trouble. This time she had to stay after class to clean the chalkboard.

"Are you certain you wouldn't like a ride home, my child?"

"Yeah Toriel, I'm fine."

Frisk felt uneasy on her walk home. She usually walked with Monster kid, but he went home sick a while ago. It wasn't very dark, but she couldn't help feeling like she wasn't alone.

 _"Human…"_

Now Frisk was really scared. She started running but something tackled her to the ground.

"HELP! SOMEBODY! ANYBODY! HE-! "

Her mouth was covered, and she was forced into a sack. She cried out in shock as she was thrown into some sort of car.

"Are you sure she already left school?"

Sans was frantic. He's been waiting for Frisk to get home for 3 hours now, and was getting more and more worried at every passing moment. He called everybody in his contacts, except for Papyrus. The last thing Frisk needed was 2 panicking brothers while she was missing, though he WILL fill him in eventually. Papyrus was at work, and Sans was waiting for him to get home first. He had a plan.

 _Earlier_

"Are you gonna look too, Sans?" Asked Undyne, over the phone.

"I'm gonna wait for Papyrus to get home. Then if frisk isn't home by then, I'll tell him what's going on. I'll ask him to stay home and call me if she comes home. But I will go out searching if Frisk isn't back by then."

"Okay, we'll keep you posted."

"Thanks Undyne."

 _Present time_

Sans hung up the phone with Toriel. He felt hot tears running down his cheek bones. All control he had was gone as he looked out the window.

"C'mon kid, where are you?"

Frisk was crying. She didn't know where she was, her knee was bleeding, and she was scared. She wanted to go home. She wanted to hear Sans' terrible puns. She wanted to hear Papyrus yelling at him for them. She wanted to eat Papyrus' terrible spaghetti. But she couldn't. she sobbed into her knees. Where were her brothers? Where they looking for her? Did they even know she was gone? She was sure Sans was. She gets yelled at if she was 1 minute late. And here we are, 3 hours late, 4 hours- 5 hours. She had no idea how long it's been. All she knew was that she wanted her brothers, and she wanted them now.

"Sans….. Paps…. Please, I'm so scared. I need you… I'm alone, and I'm scared… please…"

Then she drifted off to sleep.

"She's in here, Mr. G!"

Frisk woke up with a start. Her kidnappers were on their way to her holding cell.

"nonononononononononono"

Frisk was pushing herself against the wall, tears still trickling down her cheeks. Then the door swung open.

"*Gasp* No…"

Her eyes widened, her tears ran faster, the figure she saw was not one she neither expected nor wanted to see

W.D. Gaster!

End chapter 1.


	2. Chapter 2: Panic! Sans

Sans was certain that there was annoyance between his friends. He called Undyne every 15 minutes, and Alphys every 5 (she was monitoring everything). He was still crying though, so they didn't say anything. Sans jumped when the door opened and Papyrus walked in.

"SANS! HUMAN! I, _THE GREAT PAPYRUS!_ AM HOME!"

" it's now or never Sans,,, Hey, Papyrus? We need to talk."

As they talked, Sans started crying again. The cries turned into hugs. The sobs turned into hugs.

"SHHHHHHHHH… SANS CALM DOWN! IT'S ALRIGHT! EVERYTHING IS GOING TO BE OKAY!"

Sans still didn't answer. He just cried into Sans' scarf.

"BUT WHY DIDN'T YOU TELL ME SOONER?!"

"*sniff* I-I didn't w-want you to *sniffle* p-panic. That's the last thing Frisk needs right now"

"OKAY, THAT'S FAIR! SO WHAT'S THE PLAN, SANS?!"

"I'll go search. You stay here and call me if Frisk comes home before I do.

"BE CAREFUL SANS! I CAN'T LOSE YOU TOO!"

They hugged one more time before Sans teleported away.

 _Elsewhere_

Frisk was afraid. Gaster slowly walked towards her and reached his hand out to her face, which she smacked away.

 _"hello, my child."_

"What do you want from me?"

Gaster just laughed. It was a dry, heartless laugh that sends chills down Frisk's spine.

 _"Nothing, yet. But soon enough, I WILL come for your DETERMINATION!"_

Frisk practically screamed. Tears ran down her face.

"But I can't give you my DETERMINATION. I don't know how it works!"

 _"Well, that's too bad, because you don't get a bite to eat until you do."_

The door slammed shut, leaving Frisk to cry in the dark.

"Sans…. Please, help me…"

 _In town_

Sans was running through town. He didn't care what time it was or who was sleeping, he needed to find his sister, and he needed to find her fast.

"FRISK! FRISK WHERE ARE YOU!? FRISK, PLEASE?! FRISK? FRISK!"

After about 2 or 3 hours, he started wearing himself out.

"Frisk… please…. answer... me…"

He must have dozed off because the next thing he knew, he was being shaken awake by Undyne.

"Sans, wake up. SANS!"

"Huh? Wha-? Undyne?"

"Are you okay? Papyrus got worried when you didn't come home last night."

Sans yawned and stretched, wiping his eyes.

"Yeah, I'm fine. You know me; I'm usually _bone-tired"_

"Ugh, whatever. Did you find anything about Frisk?"

Sans' smile immediately faded from his face. He stared at his flanges, tears forming in his eye-sockets. Immediately, Undyne knew she struck a nerve (Or whatever, skeleton's don't have nerves), Awkwardly, she leaned in and hugged her friend. Sans hugged her back, her back and cried into the fish's shoulder.

"San, it's okay. Frisk will be okay. We'll find her and all will be great again, you'll see."

"But statistics say that after 24 hours or so after a child's disappearance, they're usually dead."

"Sans, listen to me! If you think like that, then we may as well stop searching now. Frisk will be okay; she is strong and knows how to take care of herself. We will FIND the assholes that took her and bring her home and throw their sorry asses in jail. But if you just assume she's dead or dying, then there's no point. So are you in? or are we done searching?"

"You're right, Undyne."

Sans stood up and wiped the tears off his skull.

"C'mon, let's go find my sister."

They hugged again, a little less awkwardly. And then ran off to continue searching.

End chapter 2


	3. Chapter 3: Gaster Disaster

It's been about 3 days since Frisk was kidnapped. She was scared, cold and hungry. Poor Frisk hasn't had a bite to eat since her capture, and her HP was getting low. In those 3 days she has gone through hell and back. Gaster often preformed painful experiments trying to extract her DETERMINATION. Frisk was living in constant fear, never knowing when Gaster would send his goons to come get her and take her away for another experiment. She hasn't slept much either. She was afraid of what would happen if she did. Every night she tried to get cell service to get a hold of Sans and Papyrus. She wanted to tell them she was scared, that she needed them. But so far, no dice. She was attempting for the 3rd time that night when:

"And what do you think YOU'RE doing, human?"

Frisk's eyes widened, a gasp of shock jumped out of her mouth. She turned quickly, coming face to face with the tall, cat-type creature in front of her. His bright, amber eyes staring into her brown ones. Tears were trickling down her cheeks.

"I-I-I was just-" she started, before being cut off to a harsh smack across her face.

"you know what, kid. I don't care. Come on, follow me. AND KEEP THE PHONE HERE."

Frisk was scared. She was sent off to endure more and more experiments every 3-4 hours. Most consisted of blood extraction, but sometimes he directed his attention to her soul. Frisk's soul is red, the same colour as DETERMINATION. Often, to see how much she can endure, Gaster would attack Frisk. He would then heal her HP with green magic, which doesn't help with pain or physical injuries. So Frisk was left wounded and bloody. Her favorite sweater was in tatters because she was making bandages with torn up cloth.

"I wonder what it'll be this time." She thought to herself.

That was when she arrived at the lab of which she's grown to hate. It may have only been 3 days, but it felt like 3 months.

" _Hello, Frisk. Have a seat, be a good human, and co-operate."_ He said, in his dry, un caring voice.

Frisk whimpered as she was strapped into the chair. She tried to pull free as Gaster brought the syringe closer and closer to her arm, but the cat monster stopped her. The other monster, a dog type monster, watched, snickering to himself. Frisk watched as her blood was drawn into the syringe and ejected into a peltries dish.

 _"Okay, now to see if it works."_

Gaster watched patiently as his experiment took part. He watched in awe as the DETERMINATION trickled out of the blood, as a deeper shade of red. Frisk felt sick.

 _"now… DETERMINATION can be extracted. *yawn* I'm bored. Who wants to do an… endurance test?"_

Gaster chuckled to himself, watching the horror build up in Frisk's eyes.

"D-do… I-I have a say, Mr. Gaster?"

Gaster laughed. It still sent chills down her spine. But she knew the answer. NO!

The first attack was just a basic bone attack. Frisk had no problems dodging those. It was the next attack that caused her troubles; Gaster blasters. She was hit a couple times, leaving severe burns on her arm and leg. This time Gaster almost killed her. Blood was pooling out of a deep injury on her right arm. In a normal circumstance, she would be taken to a hospital, but Gaster doesn't give a shit. He restored her HP, and had scar-face (the cat monster) take her back to her cell. She noticed him acting weird, and was surprised that he threw some things in with her. These items consisted of: a first-aid kit, a hot-cat, and a signal processing unit (SPU). He wanted her to get a hold of her brothers… weird. Immediately, Frisk hooked it up to her phone, injuries can wait, she needed to get a hold of Sans.

"Perfect!"

She got a signal. Frantically she scrolled through her phone, looking for Sans' name. she had NO hesitation pressing 'call', then waited for him to answer.

 _Sans' house_

Sans was sitting on the couch, staring at the TV. He wasn't really watching it, just… looking at it. Papyrus was worried. His lazy brother was restless. He hasn't slept, he barely eats, and if you even mention ketchup, his skull goes pale. He was shocked when suddenly he heard-

"FRISK! ARE YOU OKAY BUDDY? WHERE ARE YOU?"

Papyrus ran into the room. Sans was on the phone.

"PUT IT ON SPEAKER PHONE!" He said.

"Huh? Oh, sure bro, one sec. hold on Frisk."

"S-s-sans… Pap-pyrus… I'm scared.. I'm so scared."

Frisk's voice was weak. She was drained of all excitement and was scared and in pain. Maybe she should of helped herself first.

"Frisk, are you alright? Do you know where you are?"

Crying could be heard through the phone's speaker.

"I-I don't! I don't know where I am. And I'm not okay"

Sans and Papyrus exchanged worried glances.

"Paps, call Alphys. Tell her we have Frisk on the phone. Ask her if she can track it for us. This may be our only chance to find her."

Papyrus nodded and ran off to the phone.

"Okay, Frisk, do you at least know who has you? What they look like?"

"y-yeah, but Sans, can you promise me something?"

"Sure kid, anything."

"Don't freak out."

"'Don't freak out?' Why?"

"Just promise."

"Fine, kiddo, I promise."

"It' r…"

"Huh? Didn't quite catch that, kid."

"IT'S GASTER, SANS! GASTER HAS ME!"

Sans gasped in shock. He froze for a second. That was NOT the name he was expecting.

"Paps, it's worse than we thought…"

"WHAT IS IT SANS?"

"Gaster's got her."

"WHAT!? ALPHYS, YOU NEED TO HURRY! FRISK MAY NOT HAVE MUCH TIME LEFT!"

Sans grew silent. He was listening to Frisk telling him about all of the horrible things she endured. The experiments, the beatings, the 'endurance tests' and about her recent sufferings, her burns from the blasters, everything. Then the fax machine went off.

"What the- is that the fax machine?"

"ALPHYS MUST HAVE GOTTEN THE ADRESS."

Sans ran to the machine and cheered,

"YES! This is it! Hang on Frisk, I'm coming!"

Papyrus noticed as Sans made a break for the door, cutting him off.

"HOLD ON SANS! YOU ARE NOT GOING ALONE!"

"Than what do YOU suggest?"

"LET'S CALL OUR FRIENDS. POOR FRISK NEEDS ALL THE HELP SHE CAN GET."

"Alright bro. here's the deal. You call Undyne and Mettaton. I'll call Muffet and the Dreemurrs. Not all of us will go. We'll plan it all out when they get here, okay?"

"UH-HUH."

"Okay then, let's call them. Then we'll go straight for Frisk and bring her HOME."

End chapter 3


	4. Chapter 4: The fight for Frisk

Frisk was happy. She was finally getting out of this hellhole. Sans was on his way, she knew he was. She decided to turn her attention to her wound; she took a cloth out of the first-aid kit, dipped it in her water, and cleaned it. It stung, but at least it was clean. After an hour, Frisk began to worry.

"Please come quickly Sans… Please."

"HEY KID! COME HERE!"

Frisk's head shot up. There were Gaster's lackeys were right there. In a panic, she backed away.

"C'mon Sans, where are you?"

Angrily, the dog monster grabbed her by the arm. He yanked her forward and she fell to the ground, re injuring her knee. He then kicked her in the side.

"Get up, you rotten piece of dog residue!"

Frisk just whimpered she couldn't really breathe, and was in a lot of pain. That 1 blow did 5 damage and it hurt.

"I SAID GET UP!" he yelled, kicking her harder.

Frisk screamed in pain, begging him to stop.

"Hey dog-breath. Why don't you do as the kid says and leave her alone?"

Frisk's head turned towards the voice. Her face was soaked in blood and tears.

"Sans?"

"NEVER FEAR HUMAN! WE HAVE COME TO RESCUE YOU!"

"Papyrus?"

Sans' eye started glowing blue. He used his magic to lift both monsters off the ground. He pinned them to a wall, spawned his blasters, and took aim.

"Sans! Don't, please!"

He looked over his shoulder. Frisk was trying to stand, with a little bit of help from Papyrus.

"Really kid? After everything they put you through, after all the torture and torment from these past 4 days, and you still want to spare them?"

"It isn't their fault. They are as much victims in this as I am. Gaster doesn't exactly have 2 respectful volunteers here Sans."

Reluctantly, Sans lowered them to the ground, though not without-

"MUFFET!"

"Of course dearie! One spider web coming up!"

Yep. They were tied up in spider webs. Papyrus picked Frisk up and they all ran out.

"Look out! He's coming!"

Muffet crawled to the ceiling, Sans positioned himself in front of his siblings, and Mettaton and Undyne ran to either side of him.

 _"My, my. What a fascinating discovery. Hello Sans, Papyrus. How good to see you."_

Sans aimed his Gaster blaster in response. Papyrus held Frisk to him even tighter. Undyne and Mettaton also prepared for a fight. Sans fired his blaster head on. Undyne charged forwards, swinging her spears, missing every time.

"Frisk. It would be great to know his stats right about now!"

Frisk pressed the "ACT" button.

"W.D. Gaster. 3 attack 5 defense, but don't let the low stats fool you. This foe is a master dodger and is really fast."

"Shit… Well, better get fighting boys." Undyne groaned.

Mettaton transformed into Mettaton NEO and the battle began. Frisk didn't want her brother fighting. Sans' HP was too low. But she was too weak to stay awake. She was cold, she felt sick, she hurt, and she was tired. She shivered ass she slowly lost consciousness in Papyrus' arms. Gaster was getting cocky. He dodged attacks with a smile, avoided blasts with a laugh, and was only hit twice so far (not including Sans' Gaster blaster at the start of the fight).

"SANS!"

Sans turned his attention towards his brother for a second.

"Yeah bro?"

"TAG ME IN AND TAKE FRISK. YOUR HP IS TOO LOW FOR THIS FIGHT."

"Okay, fine."

Sans gently took the sleeping Frisk into his arms, startled at how light she was. And how cold she felt.

"Geez kid. If I didn't know better, I would guess you were dead."

She wasn't, of course. Sans knew this for sure because she was shivering like mad. Sans took off his sweater and draped it on her, like a blanket. Knowing that she was at least warm, Sans turned his attention back to the fight.

Things were going well. Sans could see Gaster's health getting low. He had about 17HP out of 30. Sans spawned his Gaster blaster again and told it to attack Gaster only. He trusted it to go in alone because he couldn't join it. The blaster fired, draining Gaster down to 10HP.

"Better make things easier for them though."

He looked up at Muffet and signaled her. Muffet nodded and went at it. In a few moments, Gaster was webbed.

"who wants to do the honors?"

"I do."

Everyone moved out of the way, letting sans get to Gaster.

 _"San, my son. Please don't do this…"_ Gaster pleaded.

"You are no father of mine. You see this child? This child that you've tormented for the past 4 days? I may call her my sister, but she's legally my daughter. This makes her your granddaughter. And you being the bastard you are, you don't even care. You didn't care when it came to leaving us, and you didn't care when it came to hurting Frisk. I hate you."

Then he spawned his instant kill attack. He watched as Gaster dusted in front of him.

"Get, dunked on." He said, completely straight faced and serious. "Come on guys, let's go."

End of chapter 4


	5. Chapter 5: Epilogue

"C'mon kid. Take your medicine."

Sans and Papyrus were trying to get Frisk to take some cold medicine. To their dismay, she was being stubborn.

"*sigh* C'mon Frisk, if you take your medicine, you'll feel better in _sick-onds_."

"SANS! I JUST- CAN'T EVEN- UGH, I'M MAKING SOUP."

Frisk actually did laugh at that joke. Sans took it as an opportunity.

"Ha ha ha ha h- _urk_." She literally gagged.

"Sorry kiddo. Had to do it the hard way." He smirked.

Papyrus walked away. He was going to make the soup he promised. This gave her the perfect opportunity to talk to Sans.

"Sans."

"Yeah kid?"

"Can we talk?"

Sans just stared at her for a second. He was confused about what she may have wanted to talk about, so he decided to hear her out.

"Sure kid, always."

"You are probably going to hate me for this but-"

"Frisk, I will NEVER hate you, EVER."

"I was losing DETERMINATION Sans. You hung up the phone saying you'll be right there, but you weren't there for an hour. To be honest, I started thinking you weren't coming at all. For the first time in my life, I felt completely, undetermined."

Sans was taken aback from that statement. He actually felt hurt.

"Frisk, listen to me. I would never abandon you, ever. I may call you my sister. But you are legally my daughter. I would move mountains for you, Frisk. If you are in danger, or in need of any help at all, I WILL be there to save you. I'll always be by your side, Frisk. I love you, I always will. *sigh* Get some sleep kiddo, you'll feel better in no time. But don't worry, I'll wake you up for some of Paps' soup, 'kay?"

Frisk nodded, smiling. She yawned as she settled into her covers. Though there was pain. It's been 2 days, and she was still in a lot of pain. About 15 minutes later, Sans walked in with a tray. On the tray, there was some soup and a glass of water. He gently shook the sleeping child awake.

"Hey, Frisk. Soup's on."

"Mmmm… not hungry, just sleepy..." She groaned.

Sans got a little annoyed. That was before he noticed her face was pale. Checking her forehead, he noticed she was a little warm.

"Tsk. You have a bit of a fever. Hang tight kid I'll be back."

He came back with a thermometer. After checking her temperature, he found it read 103.2oF.

"Geez kid. You're a walking heater. How'd you get so sick so fast?"

Frisk only groaned. Sighing, Sans pulled out his phone and started dialing Alphys's number when-

"*cough, cough, cough, cough.*"

Putting down his phone for a second, he started rubbing Frisk's back to help suppress the coughs. Then he grabbed his phone and dialed her number more urgently. She arrived 3 minutes later.

"O-o-oh d-dear. But d-don't worry Sans, it's just the flu. S-she'll be f-fine."

Sans looked relieved.

"Heh. I guess she won't be going to school any time soon…"

 _Later on_

It's been 2 weeks since Frisk's rescue. She recovered from her illness, and some of her injuries completely healed. This means, it's time to go back to school. Naturally, Frisk was reluctant. She knew Gaster was dead, but she was still scared.

"You okay kid?" Sans asked her, noticing the resistance to leaving for school.

"Huh? Oh, yeah. I'm fine."

Sans chuckled to himself.

"Nervous?"

Frisk just stared at the floor.

"Heh, don't sweat it kid. I'll walk ya."

She happily agreed. On the walk to school, Frisk asked sans if she could put on a violin recital for all of their friends.

"Sure kid, you got a real knack for it."

"Yay! Thanks Sans! Hey, I got an idea!"

"What's up kiddo?"

"Maybe you can play them a song too."

"Maybe, if you let me touch your violin."

Then they told jokes the rest of the way there.

THE END


End file.
